Inkjet and laser printers have become commonplace and necessary computing peripherals in most workplace and home computing environments. Today, many printers are multi-functional sophisticated image forming devices capable of printing images on a large array of recording media such as letterhead, paper envelopes and a host of other media. Over the years, printer performance has improved greatly in terms of resolution, number of pages printed per minute, document feeding options, copying capabilities and other qualifiers of a printer's performance. One particular indicator of a printer's performance that is becoming an important selling point is the time to first copy, which is an indicator of how long it takes to print a first sheet from a stand-by or power conserving state.
In an electrophotographic (EP) printer, unfused toner particles are electrostatically attracted to the media to form an image. In order for the image to be fixed permanently the media must be fused. A fuser combines high temperature and pressure to the toner until it is melted and forced to adhere to the media. As such, the fuser is a critical component in the overall image forming process of most EP image forming devices.
The time to print the first sheet can be reduced by maintaining the instant-on fuser temperature at a “ready” temperature while not printing. This temperature is just warm enough to prevent the fuser from being the primary delay in the time to first copy. Otherwise, if the fuser is off there is typically delay, perhaps as much as two seconds, for the fuser to warm up for a particular print job.
A problem that can arise from maintaining a printer in this type of “ready mode” is the amount of visible light flicker that results while the fuser is being kept warm. Applying energy to a fuser heating element, be it a lamp or ceramic heater, draws enough current to cause a flicker affect on incandescent or fluorescent lighting coupled to the same electrical circuit as the printer. This can be particularly annoying since the flicker occurs while the printer is in ready mode and yet the printer is perceived by the user to be idle.
The amount of flicker can be considerably reduced by controlling the fuser with a phase control method. This method of fuser control conducts current across a variable portion of each AC waveform half cycle, thus reducing the amount of in-rush current to the fuser assembly. The problem with phase control is that it tends to cause difficulty in passing Electro Magnetic Control (“EMC”) harmonics specifications.
At the same time, the specifications on flicker and EMC harmonics levels vary across different geographies. In Europe and other regions that use 220 volt line voltage, the amount of in-rush current is not as great as that on 120 volt devices. As such, a printer operating in a 220 volt region will most likely meet the flicker requirements without having to use phase control. Instead, the engine can use integer half cycle control, which has no problems in meeting the EMC harmonics requirements.
However, in the U.S. and other geographies that use a 120-volt power supply, the current draw of the heater is higher and causes annoying light flicker when using integer half cycle control. Although there is no specification for flicker in these regions, the issue is addressed for customer satisfaction purposes by using the phase control method. EMC harmonics specifications are met by adding filtering components (i.e. an inductor choke, for example) to the low volt power supply.
Likewise, Japanese models exhibit flicker when integer half cycle control is used with its 100-volt power supply. However, when using phase control, the printer can not meet the industry harmonics standards for that region even with the modifications to the low volt power supply. Therefore, integer half cycle must be used even though it results in flicker. Although there is no flicker standard in Japan, it can prove to be an annoyance to the customer, especially while the printer is not printing and is keeping the fuser warm in ready mode. To eliminate this, the fuser ready mode control needs to be disabled such that the fuser turns off immediately after a warm up condition or upon completion of a print job. Because ready mode is disabled on this model, it will not have optimal first copy time, but this is an accepted compromise to eliminate flicker while not printing.
Since the specifications vary across different geographies as to the limits on flicker and EMC harmonics levels, a need exists for a means of determining what type of fuser control should be used based on the geographic location of a printer. At the same time, such a means would have to consider whether to enable or disable the fuser ready mode.
References in the detailed description below refer to like references in the figures, unless otherwise indicated.